This invention relates to forming a hafnium oxide film on a substrate by chemical vapor deposition.
A number of materials have been proposed as replacements for silicon dioxide as the gate dielectric in metal oxide semiconductor field effect transistors (MOSFETs). Examples include oxides of titanium, zirconium, and hafnium. These materials have higher dielectric constants than silicon dioxide, making it possible to achieve an equivalent capacitance using a thicker layer. The thicker layer, in turn, reduces leakage current.
In general, the invention features a process for forming a hafnium oxide-containing film on a substrate such as silicon that includes introducing an anhydrous hafnium nitrate-containing precursor into a reactor containing the substrate, and converting the precursor into the hafnium oxide-containing film on the substrate by chemical vapor deposition. The precursor may be introduced into the reactor in the form of a gas or a liquid. It may be used alone or in combination with a carrier gas such as nitrogen. The hafnium nitrate may be used as a single source precursor or in the presence of an additional oxygen source such as oxygen (O2), ozone (O3), water (H2O) or hydrogen peroxide (H2O2).
Using a hafnium nitrate-containing precursor eliminates the need for a separate oxidizing agent such as oxygen. In addition, because the precursor is free of carbon, hydrogen, and halogen atoms, impurities in the final film are minimized.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.